Method of manufacturing square secondary battery

ABSTRACT

A method of manufacturing a secondary battery including an electrode body element fabricating step in which a first electrode body element including a positive electrode plate and a negative electrode plate, and a second electrode body element including a positive electrode plate and a negative electrode plate are fabricated, a tab-connecting step in which a first positive electrode tab group of the first electrode body element and a second positive electrode tab group of the second electrode body element are connected to a second positive electrode collector, and a first negative electrode tab group of the first electrode body element and a second negative electrode tab group of the second electrode body element are connected to a second negative electrode collector, and an electrode body fabricating step in which, after the tab-connecting step, the first electrode body element and the second electrode body element are unified.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.16/335,750, filed Mar. 22, 2019, which is a National Stage Entry ofInternational Application No. PCT/JP2017/035094 filed Sep. 28, 2017,which claims the benefit of Japanese Patent Application No. 2016-192732filed in the Japan Patent Office on Sep. 30, 2016, each of which isincorporated by reference herein in its entirety.

TECHNICAL FIELD

The present invention relates to a method of manufacturing a squaresecondary battery.

BACKGROUND ART

Square secondary batteries such as alkaline secondary batteries andnonaqueous electrolyte secondary batteries are used in power sources fordriving electric vehicles (EV), hybrid electric vehicles (HEV, PHEV),and the like.

In such square secondary batteries, a battery case is configured of abottomed cylindrical square outer package including an opening and asealing plate that seals the opening. The battery case accommodatestherein an electrode body including positive electrode plates, negativeelectrode plates, and separators, and an electrolyte. A positiveelectrode terminal and a negative electrode terminal are attached to thesealing plate. The positive electrode terminal is electrically connectedto the positive electrode plates through a positive electrode collector,and the negative electrode terminal is electrically connected to thenegative electrode plates through a negative electrode collector.

The positive electrode plates each include a positive electrode corebody made of metal and a positive electrode active material mixturelayers formed on the surfaces of the positive electrode core body. Apositive electrode core body exposed portion, on which no positiveelectrode active material mixture layers is formed, is formed in aportion of the positive electrode core body. Furthermore, the positiveelectrode collector is connected to the positive electrode core bodyexposed portion. Furthermore, the negative electrode plates each includea negative electrode core body made of metal and negative electrodeactive material mixture layers formed on the surfaces of the negativeelectrode core body. A negative electrode core body exposed portion, onwhich no negative electrode active material mixture layers is formed, isformed in a portion of the negative electrode core body. Furthermore,the negative electrode collector is connected to the negative electrodecore body exposed portion.

For example, Patent Literature 1 and Patent Literature 2 disclosedisposing of an insulating spacer between an electrode body and asealing plate.

CITATION LIST Patent Literature

-   PTL 1: Japanese Unexamined Patent Application Publication No.    2005-32477-   PTL 2: Japanese Unexamined Patent Application Publication No.    2015-76293

SUMMARY OF INVENTION Technical Problem

In PTL 1 and PTL 2 described above, while disposing of the insulatingspacer between the electrode body and the sealing plate is disclosed,further improvement thereof is needed.

A main object of the present invention is to provide a secondary batterythat has a high volume energy density and that has a high reliability.

Solution to Problem

A method of manufacturing a square secondary battery according to anaspect of the present invention in which the square secondary batteryincludes an electrode body that includes a positive electrode plate anda negative electrode plate, an outer package that includes an openingand that houses the electrode body, a sealing plate that seals theopening, a positive electrode tab provided in the positive electrodeplate, a negative electrode tab provided in the negative electrodeplate, a positive electrode external terminal that is electricallyconnected to the positive electrode tab and that is attached to thesealing plate, a negative electrode external terminal that iselectrically connected to the negative electrode tab and that isattached to the sealing plate, a positive electrode collector memberthat electrically connects the positive electrode tab and the positiveelectrode external terminal to each other, a negative electrodecollector member that electrically connects the negative electrode taband the negative electrode external terminal to each other, and aninsulating member that is disposed between the sealing plate and theelectrode body, the method of manufacturing the square secondary batteryincluding an electrode body element fabricating step in which a firstelectrode body element including the positive electrode plate and thenegative electrode plate, and a second electrode body element includingthe positive electrode plate and the negative electrode plate arefabricated, a tab-connecting step in which the positive electrode tab ofthe first electrode body element is connected to the positive electrodecollector member, the negative electrode tab of the first electrode bodyelement is connected to the negative electrode collector member, thepositive electrode tab of the second electrode body element is connectedto the positive electrode collector member, and the negative electrodetab of the second electrode body element is connected to the negativeelectrode collector member, and an electrode body fabricating step inwhich, after the tab-connecting step, the first electrode body elementand the second electrode body element are unified as one so that theinsulating member is disposed between the positive electrode tab of thefirst electrode body element and the positive electrode tab of thesecond electrode body element, and between the negative electrode tab ofthe first electrode body element and the negative electrode tab of thesecond electrode body element.

With such a configuration, by disposing the insulating member at apredetermined position, an unintentional short-circuiting of thepositive and negative electrodes can be prevented. Furthermore, with themethod described above, since the insulating member can be disposed in asmaller space, the secondary battery becomes one with a higher volumeenergy density.

Advantageous Effects of Invention

According to the present invention, a secondary battery that has ahigher volume energy density and that has a higher reliability can beprovided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a square secondary battery according toan embodiment.

FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1 .

FIG. 3 is a plan view of a positive electrode plate according to theembodiment.

FIG. 4 is a plan view of a negative electrode plate according to theembodiment.

FIG. 5 is a plan view of an electrode body element according to theembodiment.

FIG. 6 is a bottom view of a sealing plate after components have beenmounted.

FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. 6 .

FIG. 8 is an enlarged view of a vicinity of a first positive electrodecollector, a second positive electrode collector, and a current breakingmechanism in FIG. 7 .

FIG. 9 is an enlarged view of a vicinity of the first negative electrodecollector and the second negative electrode collector in FIG. 7 .

FIG. 10 is a diagram illustrating a step of connecting tabs to a secondcollector.

FIG. 11 is a perspective view of the first insulating member and thesecond insulating member.

FIG. 12 is a cross-sectional view of a vicinity of a portion connectingthe first insulating member and the second insulating member to eachother, taken in a short direction of the sealing plate.

FIG. 13 is a top view of the second insulating member.

FIG. 14 is a cross-sectional view of a vicinity of a portion connectingthe negative electrode tab and the second negative electrode collectorto each other, taken in the short direction of the sealing plate.

FIG. 15 is a cross-sectional view of a sealing body, a shielding member,and a second insulating member of a square secondary battery accordingto a first modification, taken in the short direction of the sealingplate.

FIG. 16 is a cross-sectional view of a sealing body, a shielding member,and a second insulating member of a square secondary battery accordingto a second modification, taken in the short direction of the sealingplate.

FIG. 17 is a bottom view and a cross-sectional view of a shieldingmember and a second insulating member of a square secondary batteryaccording to a third modification.

FIG. 18 is a top view of a second insulating member of a squaresecondary battery according to a fourth modification.

DESCRIPTION OF EMBODIMENTS

A configuration of a square secondary battery 20 according to anembodiment will be described below. Note that the present invention isnot limited to the following embodiment.

FIG. 1 is a perspective view of the square secondary battery 20. FIG. 2is a cross-sectional view taken along line II-II in FIG. 1 . Asillustrated in FIGS. 1 and 2 , the square secondary battery 20 includesa battery case 100 formed of a bottomed and polygonal-tube-shaped squareouter package 1 including an opening, and a sealing plate 2 that sealsthe opening of the square outer package 1. The square outer package 1and the sealing plate 2 are, desirably, formed of metal and are,desirably, formed of aluminum or an aluminum alloy, for example. Astacked electrode body 3 in which a plurality of positive electrodeplates and a plurality of negative electrode plates are stacked withseparators interposed therebetween are housed in the square outerpackage 1 together with an electrolyte. A resin insulation sheet 14 isdisposed between the electrode body 3 and the square outer package 1.

Positive electrode tabs 40 and negative electrode tabs 50 are providedat an end portion of the electrode body 3 on a sealing plate 2 side. Thepositive electrode tabs 40 are electrically connected to a positiveelectrode external terminal 7 through a second positive electrodecollector 6 b and a first positive electrode collector 6 a. The negativeelectrode tabs 50 are electrically connected to a negative electrodeexternal terminal 9 through a second negative electrode collector 8 band a first negative electrode collector 8 a. Note that the firstpositive electrode collector 6 a and the second positive electrodecollector 6 b constitute a positive electrode collector member 6.Furthermore, the first negative electrode collector 8 a and the secondnegative electrode collector 8 b constitute a negative electrodecollector member 8. Note that the positive electrode collector member 6may be configured as a single component. Furthermore, the negativeelectrode collector member 8 may be configured as a single component.

The positive electrode external terminal 7 is fixed to the sealing plate2 with a resin outer side insulating member 11 interposed therebetween.The negative electrode external terminal 9 is fixed to the sealing plate2 with a resin outer side insulating member 13 interposed therebetween.The positive electrode external terminal 7 is, desirably, formed ofmetal and, more desirably, is formed of aluminum or an aluminum alloy.The negative electrode external terminal 9 is, desirably, formed ofmetal and, more desirably, is formed of copper or a copper alloy. Moredesirably, the negative electrode external terminal 9 includes a portionformed of copper or a copper alloy on an inner side of the battery case100 and a portion formed of aluminum or aluminum alloy on an outer sideof the battery case 100. Note that nickel plating or the like is,desirably, applied to a surface of the negative electrode externalterminal 9.

Desirably, a current breaking mechanism 60 that is actuated when apressure inside the battery case 100 is equivalent to or higher than apredetermined value and that breaks a conductive path between thepositive electrode plates and the positive electrode external terminal 7is provided in the conductive path between the positive electrode platesand the positive electrode external terminal 7. Note that a currentbreaking mechanism may be provided in a conductive path between thenegative electrode plates and the negative electrode external terminal9.

A gas discharge valve 17 that breaks when the pressure inside thebattery case 100 becomes equivalent to or higher than a predeterminedvalue and that discharges gas inside the battery case 100 to the outsideof the battery case 100 is provided in the sealing plate 2. The gasdischarge valve 17 is formed thinner than the other parts in the sealingplate 2. Note that the gas discharge valve 17 can be formed byperforming press working on the sealing plate 2. Alternatively, the gasdischarge valve 17 may be formed by providing a through hole for the gasdischarge valve in the sealing plate 2 and closing the through hole witha thin valve. Note that a pressure at which the gas discharge valve 17is actuated is set larger than a pressure at which the current breakingmechanism 60 is actuated.

An electrolyte injection hole 15 is provided in the sealing plate 2. Theelectrolyte injection hole 15 is sealed by a sealing plug 16 after anelectrolyte is injected inside the battery case 100 through theelectrolyte injection hole 15.

A method for manufacturing the square secondary battery 20 will bedescribed next.

[Fabrication of Positive Electrode Plate]

A positive electrode slurry containing lithium-nickel-cobalt-manganesecomposite oxide as a positive electrode active material, polyvinylidenefluoride (PVdF) as a binding agent, a carbon material as a conductiveagent, and N-methylpyrrolidone (NMP) as a dispersion medium isfabricated. The positive electrode slurry is coated on both surfaces ofa rectangular aluminum foil that is 15 μm thick and that serves as thepositive electrode core body. Subsequently, by drying the above, theN-methylpyrrolidone in the positive electrode slurry is removed and thepositive electrode active material mixture layers are formed on thepositive electrode core body. Subsequently, a compression process isperformed to compress the positive electrode active material mixturelayers to a predetermined thickness. The positive electrode plateobtained in the above manner is cut into a predetermined shape.

FIG. 3 is a plan view of a positive electrode plate 4 fabricated withthe above described method. As illustrated in FIG. 3 , the positiveelectrode plate 4 includes a main body portion in which a positiveelectrode active material mixture layer 4 b is formed on each of the twosurfaces of a rectangular positive electrode core body 4 a. The positiveelectrode core body 4 a protrudes from an edge of the main body portion.The protruded positive electrode core body 4 a constitutes the positiveelectrode tab 40. Note that the positive electrode tab 40 may be aportion of the positive electrode core body 4 a, as illustrated in FIG.3 , or another member may be connected to the positive electrode corebody 4 a as the positive electrode tab 40. Positive electrode protectivelayers 4 d, each having an electrical resistance that is larger than anelectrical resistance of each positive electrode active material mixturelayer 4 b, are desirably provided in portions in the positive electrodetab 40 adjacent to the positive electrode active material mixture layers4 b. The positive electrode protective layers 4 d desirably containceramic particles formed of alumina, silica, or zirconia, and binder.Furthermore, the positive electrode protective layers 4 d more desirablycontains conductive particles formed of a carbon material or the like.

[Fabrication of Negative Electrode Plate]

A negative electrode slurry containing graphite as a negative electrodeactive material, styrene-butadiene rubber (SBR) as a binding agent,carboxymethyl cellulose (CMC) as a thickener, and water is fabricated.The negative electrode slurry is coated on both surfaces of arectangular copper foil that is 8 μm thick and that serves as thenegative electrode core body. Subsequently, by drying the above, thewater in the negative electrode slurry is removed and the negativeelectrode active material mixture layers are formed on the negativeelectrode core body. Subsequently, a compression process is performed tocompress the negative electrode active material mixture layers to apredetermined thickness. The negative electrode plate obtained in theabove manner is cut into a predetermined shape.

FIG. 4 is a plan view of a negative electrode plates 5 fabricated withthe above described method. As illustrated in FIG. 4 , the negativeelectrode plate 5 includes a main body portion in which a negativeelectrode active material mixture layer 5 b is formed on each of the twosurfaces of a rectangular negative electrode core body 5 a. The negativeelectrode core body 5 a protrudes from an edge of the main body portion.The protruded negative electrode core body 5 a constitutes the negativeelectrode tab 50. Note that the negative electrode tab 50 may be aportion of the negative electrode core body 5 a, as illustrated in FIG.4 , or another member may be connected to the negative electrode corebody 5 a as the negative electrode tab 50.

[Fabrication of Electrode Body Element]

Stacked electrode body elements (3 a and 3 b) are fabricated byfabricating 50 positive electrode plates 4 and 51 negative electrodeplates 5 with the methods described above and by stacking the above withsquare polyolefin separators interposed in between. As illustrated inFIG. 5 , the stacked electrode body elements (3 a and 3 b) arefabricated so that, at one end portion, the positive electrode tabs 40of the positive electrode plates 4 are stacked and the negativeelectrode tabs 50 of the negative electrode plates 5 are stacked.Separators may be disposed on both outer surfaces of the electrode bodyelements (3 a and 3 b) and the electrode plates and the separators maybe fixed in a stacked state with a piece of tape or the like.Alternatively, an adhesion layer may be provided on each separator sothat the separators and the positive electrode plates 4, and theseparators and the negative electrode plates 5 are adhered to eachother.

Note that the size of the separator in plan view is, desirably, the sameas that of the negative electrode plate 5 or is larger than that of thenegative electrode plate 5. Each positive electrode plate 4 may bedisposed between two separators and after heat welding the outerperipherals of the separators, the positive electrode plates 4 and thenegative electrode plates 5 may be stacked on each other. Note that infabricating the electrode body elements (3 a and 3 b), a long separatorcan be used, and the positive electrode plate 4 and the negativeelectrode plate 5 may be stacked on each other while the long separatoris zigzag folded. Furthermore, a long separator can be used and thepositive electrode plate 4 and the negative electrode plate 5 can bestacked on each other while winding the long separator.

[Attaching Components to Sealing Plate]

Referring to FIG. 2 , and FIGS. 6 to 8 , a method of attaching thepositive electrode external terminal 7 and the first positive electrodecollector 6 a to the sealing plate 2, and a configuration of the currentbreaking mechanism 60 will be described.

The outer side insulating member 11 is disposed on an outer surface sideof a positive electrode terminal attaching hole 2 a provided in thesealing plate 2, and an inner side insulating member 10 and a cup-shapedconductive member 61 are disposed on an inner surface side of thepositive electrode terminal attaching hole 2 a. Subsequently, thepositive electrode external terminal 7 is inserted through a throughhole of the outer side insulating member 11, the positive electrodeterminal attaching hole 2 a of the sealing plate 2, a through hole ofthe inner side insulating member 10, and a through hole of theconductive member 61. Subsequently, a tip of the positive electrodeexternal terminal 7 is riveted on the conductive member 61. With theabove, the positive electrode external terminal 7, the outer sideinsulating member 11, the sealing plate 2, the inner side insulatingmember 10, and the conductive member 61 are fixed to each other. Notethat a portion of the positive electrode external terminal 7 that hasbeen riveted and the conductive member 61 are, desirably, welded to eachother by welding or the like. Furthermore, the inner side insulatingmember 10 and the outer side insulating member 11 are, desirably, eachformed of resin.

The conductive member 61 has an opening portion on an electrode body 3side. A disk-shaped deformation plate 62 is disposed so as to close theopening portion of the conductive member 61, and a peripheral edge ofthe deformation plate 62 is connected to the conductive member 61 bywelding. With the above, the opening portion of the conductive member 61is sealed by the deformation plate 62. Note that each of the conductivemember 61 and the deformation plate 62 are, desirably, formed of metaland, more desirably, are formed of aluminum or an aluminum alloy.

Subsequently, a third insulating member 63 formed of resin is disposedon the electrode body 3 side of the deformation plate 62. Desirably, thethird insulating member 63 includes a connection portion and theconnection portion is connected to the inner side insulating member 10.Furthermore, desirably, a claw-shaped hooking and fixing portion isprovided in the third insulating member 63, a flange portion, a recessedportion, or a protruded portion is provided in the conductive member 61,and the hooking and fixing portion of the third insulating member 63 isfixed to the flange portion, the recessed portion, or the protrudedportion of the conductive member 61.

Fixing projections are formed on a surface of the third insulatingmember 63 on the electrode body 3 side. Furthermore, desirably, thethird insulating member 63 includes an insulating member first area 63 xdisposed below the deformation plate 62, an insulating member secondarea 63 y that extends towards the sealing plate 2 from an end portionof the insulating member first area 63 x, and an insulating member thirdarea 63 z that extends along the sealing plate 2 from an end portion ofthe insulating member second area 63 y. An insulating member opening 63b is provided in the insulating member third area 63 z at a positionopposing the electrolyte injection hole 15 of the sealing plate 2.Furthermore, an insulating member projection 63 c that projects towardsthe electrode body 3 is provided in an edge portion of the insulatingmember opening 63 b.

Subsequently, the first positive electrode collector 6 a is disposed onthe electrode body 3 side of the third insulating member 63. The firstpositive electrode collector 6 a includes fixing through holes.Subsequently, the fixing projections of the third insulating member 63are inserted into the fixing through holes of the first positiveelectrode collector 6 a, a diameter of a distal end of each fixingprojection is enlarged, and the third insulating member 63 and the firstpositive electrode collector 6 a are fixed to each other. With theabove, fixed portions 70 are formed. As illustrated in FIG. 6 , thefixed portions 70 are, desirably, provided at four portions so as tosurround the portion connecting the deformation plate 62 and the firstpositive electrode collector 6 a to each other.

Subsequently, the deformation plate 62 and the first positive electrodecollector 6 a are connected to each other by welding through a throughhole provided in the third insulating member 63. Note that desirably,the first positive electrode collector 6 a includes a thin wall portion6 c and is connected to the deformation plate 62 by welding at the thinwall portion 6 c. Desirably, an opening is provided in the middle of thethin wall portion 6 c, and an edge portion of the opening is connectedto the deformation plate 62 by welding. Furthermore, more desirably, anannular notch is provided in the thin wall portion 6 c so as to surroundthe portion connecting the first positive electrode collector 6 a andthe deformation plate 62 to each other.

When a pressure inside the battery case 100 becomes equivalent to orhigher than a predetermined value, the deformation plate 62 becomesdeformed so that a middle portion of the deformation plate 62 movesupwards (towards a positive electrode external terminal 7 side). Withthe deformation of the deformation plate 62, the thin wall portion 6 cof the first positive electrode collector 6 a becomes broken. With theabove, the conductive path between the positive electrode plates 4 andthe positive electrode external terminal 7 becomes disconnected.

Note that a leak check of the portion connecting the conductive member61 and the deformation plate 62 to each other can be conducted byproviding a terminal through hole 7 b in the positive electrode externalterminal 7 and by having gas flow inside the current breaking mechanism60 through the terminal through hole 7 b. Furthermore, the deformationplate 62 and the first positive electrode collector 6 a can be connectedto each other by welding while the deformation plate 62 is pushedagainst the first positive electrode collector 6 a with the gas.Ultimately, the terminal through hole 7 b is sealed by a terminalsealing member 7 a. Desirably, the terminal sealing member 7 a includesa metal member 7 x and a rubber member 7 y.

The first positive electrode collector 6 a includes a collectorprojection 6 x on a surface on the electrode body 3 side.

Referring to FIGS. 2, 6, 7, and 9 , a method of attaching the negativeelectrode external terminal 9 and the first negative electrode collector8 a to the sealing plate 2 will be described.

The outer side insulating member 13 is disposed on an outer surface sideof a negative electrode terminal attaching hole 2 b provided in thesealing plate 2, and an inner side insulating member 12 and the firstnegative electrode collector 8 a are disposed on an inner surface sideof the negative electrode terminal attaching hole 2 b. Subsequently, thenegative electrode external terminal 9 is inserted through a throughhole of the outer side insulating member 13, the negative electrodeterminal attaching hole 2 b of the sealing plate 2, a through hole ofthe inner side insulating member 12, and a through hole of the firstnegative electrode collector 8 a. Subsequently, a tip of the negativeelectrode external terminal 9 is riveted on the first negative electrodecollector 8 a. With the above, the outer side insulating member 13, thesealing plate 2, the inner side insulating member 12, and the firstnegative electrode collector 8 a are fixed to each other. Note that aportion of the negative electrode external terminal 9 that has beenriveted and the first negative electrode collector 8 a are, desirably,welded to each other by laser welding or the like. Furthermore, theinner side insulating member 12 and the outer side insulating member 13are, desirably, each formed of a resin.

[Connecting Second Collector and Tab to Each Other]

FIG. 10 is a diagram illustrating a method of connecting the positiveelectrode tabs 40 to the second positive electrode collector 6 b, and amethod of connecting the negative electrode tabs 50 to the secondnegative electrode collector 8 b. Two electrode body elements arefabricated with the method described above. The electrode body elementsare referred to as the first electrode body element 3 a and the secondelectrode body element 3 b. Note that the first electrode body element 3a and the second electrode body element 3 b may have the sameconfiguration or may have different configurations. Note that theplurality of positive electrode tabs 40 of the first electrode bodyelement 3 a constitute a first positive electrode tab group 40 a. Theplurality of negative electrode tabs 50 of the first electrode bodyelement 3 a constitute a first negative electrode tab group 50 a. Theplurality of positive electrode tabs 40 of the second electrode bodyelement 3 b constitute a second positive electrode tab group 40 b. Theplurality of negative electrode tabs 50 of the second electrode bodyelement 3 b constitute a second negative electrode tab group 50 b.

The second positive electrode collector 6 b and the second negativeelectrode collector 8 b are disposed between the first electrode bodyelement 3 a and the second electrode body element 3 b. Subsequently, thefirst positive electrode tab group 40 a formed of the plurality oflayered positive electrode tabs 40 protruding from the first electrodebody element 3 a is disposed on the second positive electrode collector6 b, and the first negative electrode tab group 50 a formed of theplurality of layered negative electrode tabs 50 protruding from thefirst electrode body element 3 a is disposed on the second negativeelectrode collector 8 b. Furthermore, the second positive electrode tabgroup 40 b formed of the plurality of layered positive electrode tabs 40protruding from the second electrode body element 3 b is disposed on thesecond positive electrode collector 6 b, and the second negativeelectrode tab group 50 b formed of the layered negative electrode tabs50 protruding from the second electrode body element 3 b is disposed onthe second negative electrode collector 8 b. The first positiveelectrode tab group 40 a and the second positive electrode tab group 40b are connected to the second positive electrode collector 6 b bywelding and welded connection portions 90 are formed. The first negativeelectrode tab group 50 a and the second negative electrode tab group 50b are connected to the second negative electrode collector 8 b bywelding and the welded connection portions 90 are formed. Connecting bywelding can be performed in the following manner.

The layered tabs (the first positive electrode tab group 40 a, thesecond positive electrode tab group 40 b, the first negative electrodetab group 50 a, and the second negative electrode tab group 50 b) andthe collectors (the second positive electrode collector 6 b and thesecond negative electrode collector 8 b) are held by welding jigs fromabove and below and welding is performed. Note that the welding methodis, desirably, ultrasonic welding or resistance welding. With the above,the layered tabs and the collectors are reliably connected by welding.In a case in which the number of layered tabs is large, for example, ina case in which the number of layers is 20 or more, compared with laserwelding or the like, ultrasonic welding or resistance welding can form amore reliable welded connection portion since welding can be performedwhile interposing with a pair of welding jigs. Note that the pair ofwelding jigs are a pair of electrodes for resistance welding in a caseof resistance welding and are a horn and an anvil in a case ofultrasonic welding. Note that connecting between the tabs (the firstpositive electrode tab group 40 a, the second positive electrode tabgroup 40 b, the first negative electrode tab group 50 a, and the secondnegative electrode tab group 50 b) and the collectors (the secondpositive electrode collector 6 b and the second negative electrodecollector 8 b) can be performed by laser welding as well.

In the second positive electrode collector 6 b, the first positiveelectrode tab group 40 a of the first electrode body element 3 a isconnected on a first side with respect to a middle portion of the secondpositive electrode collector 6 b in a width direction. In the secondpositive electrode collector 6 b, the second positive electrode tabgroup 40 b of the second electrode body element 3 b is connected on asecond side with respect to the middle portion of the second positiveelectrode collector 6 b in the width direction.

In the second negative electrode collector 8 b, the first negativeelectrode tab group 50 a of the second electrode body element 3 b isconnected on the first side with respect to a middle portion of thesecond negative electrode collector 8 b in the width direction. In thesecond positive electrode collector 6 b, the second negative electrodetab group 50 b of the second electrode body element 3 b is connected onthe second side with respect to the middle portion of the secondpositive electrode collector 6 b in the width direction.

As illustrated in FIG. 10 , an opening portion 6 z is provided in thesecond positive electrode collector 6 b. After connecting the secondpositive electrode collector 6 b to the first positive electrodecollector 6 a, the opening portion 6 z is disposed at a positioncorresponding to the electrolyte injection hole 15 provided in thesealing plate 2. Furthermore, the first positive electrode tab group 40a of the first electrode body element 3 a is, with respect to theopening portion 6 z, connected on the first side in the width directionof the second positive electrode collector 6 b. Furthermore, the secondpositive electrode tab group 40 b of the second electrode body element 3b is, with respect to the opening portion 6 z, connected on the secondside in the width direction of the second positive electrode collector 6b. When the second positive electrode collector 6 b, the first positiveelectrode tab group 40 a, and the second positive electrode tab group 40b are viewed in a direction perpendicular to the sealing plate 2,desirably, portions of the first positive electrode tab group 40 a andthe second positive electrode tab group 40 b that are disposedsubstantially parallel to the second positive electrode collector 6 b donot overlap the opening portion 6 z. With the above, the second positiveelectrode collector 6 b, the first positive electrode tab group 40 a,and the second positive electrode tab group 40 b can be prevented frominterrupting the injection of the electrolyte.

Note that either of the step of fixing the first positive electrodecollector 6 a and the first negative electrode collector 8 a to thesealing plate 2 and the step of connecting the positive electrode tabs40 and the negative electrode tabs 50 to the second positive electrodecollector 6 b and the second negative electrode collector 8 b can beperformed first.

[Connecting First Positive Electrode Collector and Second PositiveElectrode Collector to Each Other]

As illustrated in FIGS. 6 and 7 , the first positive electrode collector6 a is provided with the collector projection 6 x. Furthermore, asillustrated in FIG. 10 , a collector opening 6 y is provided in thesecond positive electrode collector 6 b. As illustrated in FIGS. 7 and 8, the second positive electrode collector 6 b is disposed on the thirdinsulating member 63 so that the collector projection 6 x of the firstpositive electrode collector 6 a is positioned inside the collectoropening 6 y of the second positive electrode collector 6 b.Subsequently, edge portions of the collector projection 6 x of the firstpositive electrode collector 6 a and the collector opening 6 y of thesecond positive electrode collector 6 b are welded to each other byprojecting an energy ray such as a laser. With the above, the firstpositive electrode collector 6 a and the second positive electrodecollector 6 b are connected to each other. Note that a collector firstrecessed portion 6 f is provided around the collector opening 6 y of thesecond positive electrode collector 6 b. In other words, the collectoropening 6 y is formed in the middle of the collector first recessedportion 6 f. The first positive electrode collector 6 a and the secondpositive electrode collector 6 b are connected to each other by weldingin the collector first recessed portion 6 f.

As illustrated in FIG. 8 , the second positive electrode collector 6 bincludes a collector first area 6 b 1, a collector second area 6 b 2,and a collector third area 6 b 3. The positive electrode tabs 40 areconnected to the collector first area 6 b 1. The first positiveelectrode collector 6 a is connected to the collector third area 6 b 3.The collector second area 6 b 2 connects the collector first area 6 b 1and the collector third area 6 b 3 to each other. Furthermore, in thedirection perpendicular to the sealing plate 2, a distance between thesealing plate 2 and the collector first area 6 b 1 is smaller than adistance between the sealing plate 2 and the collector third area 6 b 3.With such a configuration, the space occupied by collector portions canbe decreased and the square secondary battery becomes one with a highervolume energy density.

As illustrated in FIG. 10 , target holes 6 e are provided in the secondpositive electrode collector 6 b on both sides of the collector opening6 y. When the first positive electrode collector 6 a and the secondpositive electrode collector 6 b are welded to each other by projectingan energy ray such as a laser, desirably, the target holes 6 e aretargets for image correction. Desirably, images of the target holes 6 eare detected, position correction is performed, and an energy ray isprojected along the shape of the collector opening 6 y. Note that ratherthan being through holes, the target holes 6 e can be recessed portions.Desirably, an area of the target holes 6 e in plan view is smaller thanan area of the collector opening 6 y in plan view. Furthermore, in thewidth direction of the second positive electrode collector 6 b,desirably, the collector opening 6 y and the target holes 6 e aredisposed on a straight line.

As illustrated in FIG. 8 , a collector second recessed portion 6 w isformed on a surface of the first positive electrode collector 6 a thatopposes the third insulating member 63 and on a back side of thecollector projection 6 x. It is desirable since, with the above, alarger welded connection portion can be readily formed between the firstpositive electrode collector 6 a and the second positive electrodecollector 6 b. Furthermore, owing to the formation of the collectorsecond recessed portion 6 w, the third insulating member 63 can beprevented from being damaged by heat during welding when the firstpositive electrode collector 6 a and the second positive electrodecollector 6 b are connected to each other by welding.

As illustrated in FIG. 8 , desirably, a distal end of the insulatingmember projection 63 c of the third insulating member 63 on the lowerside (the electrode body 3 side) protrudes to the lower side (theelectrode body 3 side) with respect to an underside of the secondpositive electrode collector 6 b around the opening portion 6 z. Withthe above, the sealing plug 16 and the second positive electrodecollector 6 b can be reliably prevented from coming in contact with eachother. Note that the insulating member projection 63 c is, desirably,annular. However, the insulating member projection 63 c does notnecessarily have to be annular and may have a partially cut away shape.

[Connecting First Negative Electrode Collector and Second NegativeElectrode Collector to Each Other]

As illustrated in FIGS. 6 and 7 , the first negative electrode collector8 a is provided with a collector projection 8 x. Furthermore, asillustrated in FIGS. 9 and 10 , the second negative electrode collector8 b is provided with a collector opening 8 y. As illustrated in FIG. 9 ,the second negative electrode collector 8 b is disposed on the innerside insulating member 12 so that the collector projection 8 x of thefirst negative electrode collector 8 a is positioned inside thecollector opening 8 y of the second negative electrode collector 8 b.Subsequently, edge portions of the collector projection 8 x of the firstnegative electrode collector 8 a and the collector opening 8 y of thesecond negative electrode collector 8 b are welded to each other byprojecting an energy ray such as a laser. With the above, the firstnegative electrode collector 8 a and the second negative electrodecollector 8 b are connected to each other. Note that as illustrated inFIG. 10 , a collector first recessed portion 8 f is provided around thecollector opening 8 y of the second negative electrode collector 8 b. Inother words, the collector opening 8 y is formed in the middle of thecollector first recessed portion 8 f. The first negative electrodecollector 8 a and the second negative electrode collector 8 b areconnected to each other by welding in the collector first recessedportion 8 f. Furthermore, similar to the second positive electrodecollector 6 b, target holes 8 e are provided in the second negativeelectrode collector 8 b.

As illustrated in FIG. 9 , a collector second recessed portion 8 w isformed on a surface of the first negative electrode collector 8 a thatopposes the inner side insulating member 12 and on a back side of thecollector projection 8 x. It is desirable since, with the above, alarger welded connection portion can be readily formed between the firstnegative electrode collector 8 a and the second negative electrodecollector 8 b. Furthermore, owing to the formation of the collectorsecond recessed portion 8 w, the inner side insulating member 12 can beprevented from being damaged by heat during welding when the firstnegative electrode collector 8 a and the second negative electrodecollector 8 b are connected to each other by welding.

As illustrated in FIG. 9 , the second negative electrode collector 8 bincludes a collector first area 8 b 1, a collector second area 8 b 2,and a collector third area 8 b 3. The negative electrode tabs 50 areconnected to the collector first area 8 b 1. The first negativeelectrode collector 8 a is connected to the collector third area 8 b 3.The collector second area 8 b 2 connects the collector first area 8 b 1and the collector third area 8 b 3 to each other. Furthermore, in thedirection perpendicular to the sealing plate 2, a distance between thesealing plate 2 and the collector first area 8 b 1 is smaller than adistance between the sealing plate 2 and the collector third area 8 b 3.With such a configuration, the space occupied by collector portions canbe decreased and the square secondary battery becomes one with a highervolume energy density.

Note that each of the collector projection 6 x and the collectorprojection 8 x are, desirably, not a perfect circle and are, desirably,square, elliptical, or track shaped.

<Connecting First Insulating Member and Second Insulating Member to EachOther>

Desirably, a first insulating member and a second insulating member areconnected after, as described above, electrically connecting thepositive electrode tabs 40 and the positive electrode external terminal7 to each other and electrically connecting the negative electrode tabs50 and the negative electrode external terminal 9 to each other.

FIG. 11 is a perspective view of the inner side insulating member 12serving as the first insulating member, and a second insulating member80. The inner side insulating member 12 includes a first insulatingmember main body portion 12 a that opposes an inner surface of thesealing plate 2. Desirably, the first insulating member main bodyportion 12 a is plate shaped. The first insulating member main bodyportion 12 a includes a through hole 12 d, and the negative electrodeexternal terminal 9 is inserted in the through hole 12 d. A pair offirst sidewalls 12 b that protrude towards the electrode body 3 areprovided at both ends of the first insulating member main body portion12 a of the inner side insulating member 12 in a short direction. Arecessed portion 12 e for connection is provided in an outer surface ofeach of the pair of first sidewalls 12 b. Furthermore, a pair of secondsidewalls 12 c that protrude towards the electrode body 3 are providedat both ends of the first insulating member main body portion 12 a ofthe inner side insulating member 12 in a longitudinal direction.

The second insulating member 80 includes a second insulating member mainbody portion 80 a disposed so as to oppose the sealing plate 2. Thesecond insulating member main body portion 80 a is disposed between thesealing plate 2 and the electrode body 3. In the longitudinal directionof the sealing plate 2, the second insulating member main body portion80 a includes, in the middle thereof, a wide-width portion 80 a 1 and,on both sides of the wide-width portion 80 a 1, narrow-width portions 80a 2 that has a width that is smaller than a width of the wide-widthportion 80 a 1. A pair of sidewalls 80 b that extend from the secondinsulating member main body portion 80 a towards the sealing plate 2 areprovided at both ends of the wide-width portion 80 a 1 of the secondinsulating member main body portion 80 a in the short direction of thesealing plate 2. Furthermore, a pair of connection portions 80 c thatextend from the second insulating member main body portion 80 a towardsthe sealing plate 2 are provided at both ends of the wide-width portion80 a 1 of the second insulating member main body portion 80 a in theshort direction of the sealing plate 2. Note that each sidewall 80 b andthe corresponding connection portion 80 c are provided with a gap inbetween in the longitudinal direction of the sealing plate 2. With theabove, since the pair of connection portions 80 c can be readilydeformed, when the connection portions 80 c are connected to the innerside insulating member 12 serving as the first insulating member, thesecond insulating member 80 can be reliably prevented from being damagedor broken.

Upper ends of the sidewalls 80 b are, desirably, in contact with theinner surface of the sealing plate 2. Note that a height of eachsidewall 80 b (a length from the second insulating member main bodyportion 80 a to the upper end of each sidewall 80 b) can be larger thana height of each connection portion 80 c (a length from the secondinsulating member main body portion 80 a to an upper end of eachconnection portion 80 c).

FIG. 12 is a cross-sectional view of a vicinity of a portion connectingthe inner side insulating member 12 serving as the first insulatingmember, and the second insulating member 80 to each other, which istaken in the short direction of the sealing plate. The connectionportions 80 c of the second insulating member 80 each include a verticalwall 80 c 1 that extends from the second insulating member main bodyportion 80 a of the second insulating member 80 towards the sealingplate 2, and a projection 80 c 2 that projects from inner lateralsurface of the vertical wall 80 c 1 towards the inner side insulatingmember 12 serving as the first insulating member. Furthermore, the aboveprojections 80 c 2 are fitted to the recessed portions 12 e forconnection of the inner side insulating member 12 serving as the firstinsulating member. With the above, the inner side insulating member 12serving as the first insulating member and the second insulating member80 are connected to each other. Note that recessed portions forconnection may be provided in end portions of the first sidewalls 12 bof the inner side insulating member 12 serving as the first insulatingmember on the sealing plate 2 side, and projections 80 c 2 may bedisposed between the inner side insulating member 12 serving as thefirst insulating member and the sealing plate 2.

Desirably, a metal plate 81 serving as a shielding member is disposed inthe second insulating member 80 at a position opposing the gas dischargevalve 17 provided in the sealing plate 2.

FIG. 13 is a top view of the second insulating member 80. Note that thebroken line in FIG. 13 indicates an outer peripheral edge of the metalplate 81. In the second insulating member 80, the metal plate 81 ismolded inside the second insulating member 80 made of resin.

The metal plate 81 is, desirably, formed of iron, an iron alloy such asstainless steel, copper, a copper alloy, aluminum, an aluminum alloy, orthe like. Note that the melting point of the metal plate 81 is,desirably, higher than the melting point of the sealing plate 2. Forexample, desirably, the sealing plate 2 is formed of aluminum or analuminum alloy, and the metal plate 81 is formed of stainless steel.

<Fabrication of Electrode Body>

The first positive electrode tab group 40 a, the second positiveelectrode tab group 40 b, the first negative electrode tab group 50 a,and the second negative electrode tab group 50 b are curved so that anupper surface of the first electrode body element 3 a and an uppersurface of the second electrode body element 3 b illustrated in FIG. 10are in contact with each other directly or with another memberinterposed therebetween. With the above, the first electrode bodyelement 3 a and the second electrode body element 3 b are unified as asingle electrode body 3. Note that the first electrode body element 3 aand the second electrode body element 3 b are, desirably, unified as onewith a piece of tape or the like. Alternatively, the first electrodebody element 3 a and the second electrode body element 3 b are unifiedas one by being disposed inside the insulation sheet 14 formed in a boxshape or a bag shape.

<Assembling Square Secondary Battery>

The electrode body 3 that is attached to the sealing plate 2 is coveredwith the insulation sheet 14 and is inserted into the square outerpackage 1. Note that the insulation sheet 14 is, desirably, aninsulation sheet bent and formed into a box shape or a bag shape.Subsequently, the sealing plate 2 and the square outer package 1 areadhered to each other by laser welding or the like and the opening ofthe square outer package 1 is sealed. After the above, a nonaqueouselectrolyte solution containing an electrolyte solvent and electrolytesalt is injected through the electrolyte injection hole 15 provided inthe sealing plate 2. Subsequently, the electrolyte injection hole 15 issealed with the sealing plug 16.

<About Square Secondary Battery 20>

In the square secondary battery 20, the second insulating member 80 isconnected to the inner side insulating member 12 serving as the firstinsulating member fixed to the sealing plate 2. Accordingly, the secondinsulating member 80 can be suppressed from moving greatly inside thebattery case 100 when a vibration or an impact is applied to the squaresecondary battery 20. Accordingly, unexpected short-circuiting that maybe caused by positional displacement of the second insulating member 80can be prevented reliably. Alternatively, the second insulating member80 can be prevented from moving inside the battery case 100 and damagingthe positive electrode tabs 40 or the negative electrode tabs 50.

Note that, desirably, one of the narrow-width portions 80 a 2 of thesecond insulating member 80 is disposed between the first positiveelectrode tab group 40 a and the second positive electrode tab group 40b, and the other one of the narrow-width portions 80 a 2 of the secondinsulating member 80 is disposed between the first negative electrodetab group 50 a and the second negative electrode tab group 50 b.Furthermore, in the longitudinal direction of the sealing plate 2,desirably, the wide-width portion 80 a 1 of the second insulating member80 is disposed between the first positive electrode tab group 40 a andthe second positive electrode tab group 40 b, and the first negativeelectrode tab group 50 a and the second negative electrode tab group 50b. With such a configuration, the second insulating member 80 can bereliably prevented from damaging the tabs. Note that the secondinsulating member 80 do not necessarily need to have the wide-widthportion and the narrow-width portions.

The pair of sidewalls 80 b that extend from the second insulating membermain body portion 80 a towards the sealing plate 2 are provided at bothends of the wide-width portion 80 a 1 of the second insulating membermain body portion 80 a of the second insulating member 80 in the shortdirection of the sealing plate 2. With such a configuration, a flow pathof gas can be reliably secured between the second insulating member mainbody portion 80 a of the second insulating member 80 and the sealingplate 2. In other words, the second insulating member main body portion80 a can be prevented from closing the gas discharge valve 17 in a morereliable manner. Accordingly, the second insulating member 80 can beprevented from interrupting the discharge of gas from the gas dischargevalve 17. Furthermore, the second insulating member 80 can be preventedfrom coming in contact with the gas valve.

In the longitudinal direction of the sealing plate 2, a length of eachsidewall 80 b is, desirably, shorter than a length of the secondinsulating member main body portion 80 a. With the above, in a case inwhich the gas discharge valve 17 is actuated, the gas generated in theelectrode body 3 can be discharged smoothly to a portion external to thebattery case 100.

Desirably, a metal plate 81 is disposed in the second insulating member80 at a position opposing the gas discharge valve 17 provided in thesealing plate 2. With the above, in a case in which abnormality occursin the square secondary battery 20, a high-temperature gas blown outfrom the electrode body 3 can be suppressed from being directly blownagainst the gas discharge valve 17. With the above, in a case in whichthe gas discharge valve 17 is broken, a high-temperature gas and sparkscan be prevented from blowing out from the gas discharge valve 17. Notethat it is practically desirable that the metal plate 81 is formed ofstainless steel.

A method of attaching the metal plate 81 to the second insulating member80 is not limited in particular. Attachment may be performed byadhering, fitting, or the like to an upper surface (a surface on thesealing plate 2 side) or the underside (a surface on the electrode body3 side) of the second insulating member 80. Furthermore, as illustratedin FIGS. 2 and 12 , the metal plate 81 may be disposed inside the secondinsulating member 80 formed of resin. With such a configuration, anunexpected short-circuiting of the positive and negative electrodesthrough the metal plate 81 can be prevented in a more reliable manner.Note that molding is desirable as a method of disposing the metal plate81 inside the resin second insulating member 80.

In the square secondary battery 20, the second insulating member 80holding the metal plate 81 is connected to the inner side insulatingmember 12 serving as the first insulating member fixed to the sealingplate 2. Accordingly, the position of the metal plate 81 can be reliablydisposed at a predetermined position and the positional displacement ofthe metal plate 81 can be suppressed. Accordingly, blowing out of thehigh-temperature gas, sparks, and the like from the gas discharge valve17 can be suppressed in a further reliable manner. Furthermore, sincethe sidewalls 80 b are provided in the second insulating member, anunexpected short-circuiting between the positive and negative electrodesthrough the metal plate 81 can be prevented in a more reliable manner.

Note that the sidewalls 80 b and the connection portions 80 c do nothave to be provided separately. For example, in the second insulatingmember 80, projections may be provided on the sidewalls 80 b and mayserve as connection portions connected to the inner side insulatingmember 12 serving as the first insulating member.

The inner side insulating member 12 serving as the first insulatingmember, and the second insulating member are, desirably, formed ofresin. For example, those formed of polypropylene, polyethylene,perfluoroalkoxy alkane (PFA), polytetrafluoroethylene (PTFE), ethylenetetrafluoro ethylene copolymer (ETFE), or the like may be used.

A through hole may be provided in the second insulating member main bodyportion 80 a of the second insulating member 80. Note that the positionwhere the through hole is provided is, in the longitudinal direction ofthe sealing plate 2, the electrolyte injection hole 15 provided in thesealing plate 2 is, desirably, provided (on a gas discharge valve 17side) with respect to the middle.

FIG. 14 is a cross-sectional view of a vicinity of the portionconnecting the first negative electrode tab group 50 a and the secondnegative electrode tab group 50 b to the second negative electrodecollector 8 b, which is taken in the short direction of the sealingplate 2. As illustrated in FIG. 14 , the first negative electrode tabgroup 50 a of the first electrode body element 3 a and the secondnegative electrode tab group 50 b of the second electrode body element 3b are each connected to the second negative electrode collector 8 b bywelding. Furthermore, the narrow-width portion 80 a 2 of the secondinsulating member 80 is disposed between the first negative electrodetab group 50 a and the second negative electrode tab group 50 b.

With such a configuration, a space S can be secured between the secondnegative electrode collector 8 b and base portions of the first negativeelectrode tab group 50 a and between the second negative electrodecollector 8 b and base portions of the second negative electrode tabgroup 50 b. The space S becomes a flow path of the gas generated insidethe electrode body 3 to the gas discharge valve 17. Accordingly, withthe configuration described above, since the gas can be smoothlydischarged to the outside of the battery case when abnormality occurs inthe square secondary battery, the square secondary battery becomes onewith a higher reliability.

In the narrow-width portion 80 a 2 of the second insulating member 80,corner portions C opposing the first negative electrode tab group 50 aor the second negative electrode tab group 50 b are, desirably, rounded.With the above, the first negative electrode tab group 50 a or thesecond negative electrode tab group 50 b can be reliably prevented frombecoming damaged by the narrow-width portion 80 a 2 of the secondinsulating member 80.

Note that similar to the negative electrode side, in the positiveelectrode side as well, the narrow-width portion 80 a 2 of the secondinsulating member 80 is disposed between the first positive electrodetab group 40 a of the first electrode body element 3 a and the secondpositive electrode tab group 40 b of the second electrode body element 3b. With the above, a space can be secured between the second positiveelectrode collector 6 b and base portions of the first positiveelectrode tab group 40 a and between the second positive electrodecollector 6 b and base portions of the second positive electrode tabgroup 40 b.

<<First Modification>>

FIG. 15 is a cross-sectional view of the sealing plate 2, a metal plate181 formed of stainless steel serving as a shielding member, and asecond insulating member 180 formed of resin in the secondary batteryaccording to a first modification taken in the short direction of thesealing plate 2.

As illustrated in FIG. 15 , the metal plate 181 is disposed between thesealing plate 2 and the electrode body 3 and at a position opposing thegas discharge valve 17. The metal plate 181 includes a shielding membermain body portion 181 a disposed so as to oppose the sealing plate 2,and a pair of shielding member lateral wall portions 181 b that extendfrom both end portions of the shielding member main body portion 181 atowards the sealing plate 2. The shielding member main body portion 181a is disposed substantially parallel to the sealing plate 2. Forexample, the inclination of the shielding member main body portion 181 aagainst the sealing plate 2 may be about −10° to 10°. The shieldingmember lateral wall portions 181 b are provided in the end portions ofthe shielding member main body portion 181 a in the short direction ofthe sealing plate 2. Note that no lateral wall portions are formed onboth end portion sides of the shielding member main body portion 181 ain the longitudinal direction of the sealing plate 2.

Furthermore, the second insulating member 180 includes a secondinsulating member main body portion 180 a disposed so as to oppose thesealing plate 2, and a pair of insulating member lateral wall portions180 b that extend from both end portions of the second insulating membermain body portion 180 a towards the sealing plate 2. The secondinsulating member main body portion 180 a is disposed substantiallyparallel to the sealing plate 2. For example, the inclination of thesecond insulating member main body portion 180 a against the sealingplate 2 may be about −10° to 10°.

The insulating member lateral wall portions 180 b are provided in theend portions of the second insulating member main body portion 180 a inthe short direction of the sealing plate 2. The shielding member mainbody portion 181 a is disposed inside the second insulating member mainbody portion 180 a, and the shielding member lateral wall portions 181 bis disposed inside the insulating member lateral wall portions 180 b. Asillustrated in FIG. 15 , the insulating member lateral wall portions 180b are in contact with the sealing plate 2 at positions that aredifferent from that of the gas discharge valve 17.

The metal plate 181 includes the pair of shielding member lateral wallportions 181 b. Accordingly, in a case in which gas with a hightemperature is blown out from the electrode body 3, when the secondinsulating member 180 is melted and the metal plate 181 moves towardsthe sealing plate 2 side, the shielding member main body portion 181 ais reliably prevented from contacting with the sealing plate 2 andclosing the gas discharge valve 17 and interrupting the discharge of thegas.

<<Second Modification>>

FIG. 16 is a cross-sectional view of the sealing plate 2, a metal plate281 formed of stainless steel serving as a shielding member, and asecond insulating member 280 formed of resin in the square secondarybattery according to a second modification taken in the short directionof the sealing plate 2.

As illustrated in FIG. 16 , the metal plate 281 is disposed in thesecond insulating member 280. Desirably, the metal plate 281 is moldedin the second insulating member 280 formed of resin. Openings 282 areformed in a surface of the second insulating member 280 on the electrodebody 3 side, and the metal plate 281 is exposed at portions where theopening 282 are provided.

<<Third Modification>>

FIG. 17 illustrates a diagram illustrating a bottom surface (a surfaceon the electrode body 3 side) of a second insulating member 380, insideof which the metal plate 381 serving as the shielding member isprovided, and illustrates a cross-sectional view taken in thelongitudinal direction, in a square secondary battery according to athird modification. Note that a portion indicated by a broken line inFIG. 17 is a position of an outer peripheral edge of the metal plate381. The second insulating member 380 includes a second insulatingmember main body portion 380 a disposed so as to oppose the sealingplate 2. The second insulating member main body portion 380 a includes awide-width portion 380 a 1, and narrow-width portions 380 a 2 providedon both sides of the wide-width portion 380 a 1.

The second insulating member 380 includes an opening 380 x at a positionwhere the metal plate 381 is disposed. The metal plate 381 is exposed inthe above opening 380 x. An exposed portion 382 of the metal plate 381is, desirably, provided at a position opposing the gas discharge valve17. A plurality of slit-shaped through holes 383 are formed in theexposed portion 382. With such a shape, while allowing the gas to bedischarged smoothly to a portion external to the battery case,high-temperature objects can be prevented from being blown out togetherwith the flammable gas to a portion external to the battery case. Notethat each through hole 383 may have a round shape, or the like.

<<Fourth Modification>>

FIG. 18 is a diagram of an upper surface (a surface on the sealing plate2 side) of a second insulating member 480 in a square secondary batteryaccording to a fourth modification.

The second insulating member 480 includes a second insulating membermain body portion 480 a disposed so as to oppose the sealing plate 2.The second insulating member main body portion 480 a includes awide-width portion 480 a 1, and a pair of narrow-width portions 480 a 2disposed on both sides of the wide-width portion 480 a 1. A width of thewide-width portion 480 a 1 in the short direction of the sealing plate 2is larger than a width of each narrow-width portion 480 a 2 in the shortdirection of the sealing plate 2. The wide-width portion 480 a 1 isdisposed at a position opposing the gas discharge valve 17 provided inthe sealing plate 2.

An insulating member through hole 485 is provided in the secondinsulating member main body portion 480 a. A position where theinsulating member through hole 485 is provided in the longitudinaldirection of the sealing plate 2 is, desirably, on the middle side ofthe sealing plate 2 with respect to the electrolyte injection hole 15provided in the sealing plate 2. Such a configuration allows theelectrolyte to be permeated to the electrode body 3 in a smoothermanner. Desirably, the position where the insulating member through hole485 is provided is a position opposing the gas discharge valve 17.

Furthermore, a groove portion 486 that extends in the longitudinaldirection of the sealing plate 2 and that is connected to the insulatingmember through hole 485 is provided in the second insulating member mainbody portion 480 a. Such a configuration allows the electrolyte to bepermeated to the electrode body 3 in a smoother manner.

Particularly, as illustrated in FIG. 2 , in a case in which the tabs(the positive electrode tabs 40 or the negative electrode tabs 50) arepositioned below and near the electrolyte injection hole 15 provided inthe sealing plate 2, and in a case in which the second insulating memberis disposed below the electrolyte injection hole 15, desirably, theelectrolyte injected through the electrolyte injection hole 15 movesinside the groove portion 486 and is injected inside the electrode body3 through the insulating member through hole 485.

Note that the groove portion 486 is, desirably, inclined in thelongitudinal direction of the sealing plate 2 so that a height thereofbecomes gradually lower towards the insulating member through hole 485.Furthermore, in the second insulating member main body portion 480 a,both sides of the groove portion 486 in the short direction of thesealing plate 2 can be inclined so that the height becomes graduallylower towards the groove portion 486.

<Others>

A gap may be provided between end portions of the separatorsconstituting the electrode body 3 on the sealing plate 2 side and thesecond insulating member 80. In other words, the end portions of theseparators constituting the electrode body 3 on the sealing plate 2 sidecan be configured so as not to be in contact with the second insulatingmember 80.

In a case in which the electrode body 3 is a stacked electrode bodyincluding a plurality of positive electrode plates and a plurality ofnegative electrode plates, and in a case in which the electrode body 3is a wound electrode body in which a winding axis thereof is disposed ina direction perpendicular to the sealing plate, front end portions ofthe positive electrode plates, front end portions of the negativeelectrode plates, and front end portions of the separators arepositioned on the sealing plate 2 side in the electrode body 3. Withsuch a configuration, in a case in which the electrolyte injection hole15 is provided in the sealing plate 2, ease of injecting the electrolyteinto the electrode body 3 is improved.

In such a case, the end portions of the separators on the sealing plate2 side, desirably, protrudes to the sealing plate 2 side with respect tothe end portions of the negative electrode active material mixturelayers in the negative electrode plates on the sealing plate 2 side.Furthermore, in the electrode body 3, the end portions of the separatorson the sealing plate 2 side, desirably, protrudes to the sealing plate 2side with respect to the end portions of the positive electrode activematerial mixture layers in the positive electrode plates on the sealingplate 2 side. Furthermore, desirably, the positive electrode plates andthe separators are adhered to each other with adhesion layers, and thenegative electrode plates and the separators are adhered to each otherwith adhesion layers. With such a configuration, the positive electrodeactive material mixture layers or the negative electrode active materialmixture layers can be reliably prevented from becoming damaged, which iscaused by the positive electrode active material mixture layers or thenegative electrode active material mixture layers coming in contact withthe second insulating member.

The current breaking mechanism can be provided in only either one of theconductive path between the positive electrode plates and the positiveelectrode external terminal 7 and the conductive path between thenegative electrode plates and the negative electrode external terminal9. In such a case, the second insulating member can only be connected tothe first insulating member on the side in which the current breakingmechanism is not provided. With the above, the load on the fragileportion of the current breaking mechanism can be reduced.

As illustrated in the embodiment described above, it is desirable thatthe current breaking mechanism is formed in the conductive path betweenthe positive electrode plates and the positive electrode externalterminal 7. In such a case, the second insulating member can beconnected to only the first insulating member on the negative electrodeside.

As illustrated in the embodiment described above, it is desirable thatthe current breaking mechanism is formed in the conductive path betweenthe positive electrode plates and the positive electrode externalterminal 7. In such a case, the entire second insulating member 80 canbe positioned on the sealing plate 2 side with respect to the endportion of the positive electrode collector member 6 on the electrodebody 3 side. With such a configuration, the square secondary batterybecomes one with a higher volume energy density.

In the embodiment described above, an example in which the currentbreaking mechanism 60 is provided in the square secondary battery hasbeen given; however, the current breaking mechanism do not have to beprovided. Furthermore, the inner side insulating member 10 and the innerside insulating member 12 may be a single component.

In the embodiment described above, an example has been given in whichthe inner side insulating member 12 disposed between the sealing plate2, and the first negative electrode collector 8 a and the secondnegative electrode collector 8 b constituting the negative electrodecollector member 8 is the first insulating member, and the secondinsulating member 80 is connected to the first insulating member. Thesecond insulating member 80 can also be connected to the thirdinsulating member 63 or the inner side insulating member 10 disposedbetween the sealing plate 2 and the positive electrode collector member6.

In the embodiment described above, an example in which the electrodebody 3 is formed of two electrode body elements 3 a and 3 b has beengiven; however, it is not limited to the above. The electrode body 3 maybe a single stacked electrode body. Furthermore, the electrode body 3may be a single wound electrode body in which a long positive electrodeplate and a long negative electrode plate having a separator interposedtherebetween are wound. Furthermore, the two electrode body elements 3 aand 3 b are each not limited to a stacked electrode body and may be awound electrode body in which a long positive electrode plate and a longnegative electrode plate having a separator interposed in between arewound.

In the embodiment described above, an example has been given in whichthe positive electrode collector member is formed of the first positiveelectrode collector and the second positive electrode collector, and thenegative electrode collector member is formed of the first negativeelectrode collector and the second negative electrode collector;however, the positive electrode collector member may be formed of asingle component, and the negative electrode collector member may beformed of a single component.

In the embodiment described above, an example has been given in whichthe metal plate 81 is attached to the second insulating member 80.However, the metal plate 81 is not an essential component.

In the embodiment described above, an example in which the firstinsulating member and the second insulating member are connected to eachother has been given; however, the first insulating member and thesecond insulating member do not have to be connected to each other.

REFERENCE SIGNS LIST

-   -   20 square secondary battery    -   1 square outer package    -   2 sealing plate    -   2 a positive electrode terminal attaching hole    -   2 b negative electrode terminal attaching hole    -   100 battery case    -   3 electrode body    -   3 a first electrode body element    -   3 b second electrode body element    -   4 positive electrode plate    -   4 a positive electrode core body    -   4 b positive electrode active material mixture layer    -   4 d positive electrode protective layer    -   40 positive electrode tab    -   40 a first positive electrode tab group    -   40 b second positive electrode tab group    -   5 negative electrode plate    -   5 a negative electrode core body    -   5 b negative electrode active material mixture layer    -   50 negative electrode tab    -   50 a first negative electrode tab group    -   50 b second negative electrode tab group    -   6 positive electrode collector member    -   6 a first positive electrode collector    -   6 c thin wall portion    -   6 x collector projection    -   6 w collector second recessed portion    -   6 b second positive electrode collector    -   6 b 1 collector first area    -   6 b 2 collector second area    -   6 b 3 collector third area    -   6 e target hole    -   6 f collector first recessed portion    -   6 y collector opening    -   6 z opening portion    -   7 positive electrode external terminal    -   7 a terminal sealing member    -   7 x metal member    -   7 y rubber member    -   7 b terminal through hole    -   8 negative electrode collector member    -   8 a first negative electrode collector    -   8 x collector projection    -   8 w collector second recessed portion    -   8 b second negative electrode collector    -   8 b 1 collector first area    -   8 b 2 collector second area    -   8 b 3 collector third area    -   8 e target hole    -   8 f collector first recessed portion    -   8 y collector opening    -   9 negative electrode external terminal    -   10 inner side insulating member    -   11 outer side insulating member    -   12 inner side insulating member    -   12 a first insulating member main body portion    -   12 b first sidewall    -   12 c second sidewall    -   12 d through hole    -   12 e recessed portion for connection    -   13 outer side insulating member    -   14 insulation sheet    -   15 electrolyte injection hole    -   16 sealing plug    -   17 gas discharge valve    -   60 current breaking mechanism    -   61 conductive member    -   62 deformation plate    -   63 third insulating member    -   63 b insulating member opening    -   63 c insulating member projection    -   63 x insulating member first area    -   63 y insulating member second area    -   63 z insulating member third area    -   70 fixed portion    -   80 second insulating member    -   80 a second insulating member main body portion    -   80 a 1 wide-width portion    -   80 a 2 narrow-width portion    -   80 b sidewall    -   80 c connection portion    -   80 c 1 vertical wall    -   80 c 2 projection    -   81 metal plate    -   90 welded connection portion    -   180 second insulating member    -   180 a second insulating member main body portion    -   180 b insulating member lateral wall portion    -   181 metal plate    -   181 a shielding member main body portion    -   181 b shielding member lateral wall portion    -   280 second insulating member    -   281 metal plate    -   282 opening    -   380 second insulating member    -   380 a second insulating member main body portion    -   380 a 1 wide-width portion    -   380 a 2 narrow-width portion    -   380 x opening    -   381 metal plate    -   382 exposed portion    -   383 through hole    -   480 second insulating member    -   480 a second insulating member main body portion    -   480 a 1 wide-width portion    -   480 a 2 narrow-width portion    -   485 insulating member through hole    -   486 groove portion

The invention claimed is:
 1. A square secondary battery including: anelectrode body that includes a positive electrode plate and a negativeelectrode plate, an outer package that includes an opening and thathouses the electrode body, a sealing plate that seals the opening, apositive electrode tab provided in the positive electrode plate, anegative electrode tab provided in the negative electrode plate, whereinthe positive electrode tab and the negative electrode tab protrudetoward the sealing plate from an edge of the electrode body facing thesealing plate, a positive electrode external terminal that iselectrically connected to the positive electrode tab and that isattached to the sealing plate, a negative electrode external terminalthat is electrically connected to the negative electrode tab and that isattached to the sealing plate, a positive electrode collector memberthat electrically connects the positive electrode tab and the positiveelectrode external terminal to each other, a negative electrodecollector member that electrically connects the negative electrode taband the negative electrode external terminal to each other, aninsulating member that is disposed between the sealing plate and theelectrode body, a gas discharging valve that is provided in the sealingplate, wherein the insulating member includes: a first region which islocated between the sealing plate and a collector member selected fromthe positive electrode collector member and the negative electrodecollector member, and a second region which is located between the gasdischarging valve and the electrode body, wherein the second regionoverlaps the gas discharging valve.
 2. The square secondary batteryaccording to claim 1, wherein the electrode body includes: a firstelectrode body element which has a positive electrode plate and anegative electrode plate, and a second electrode body element which hasa positive electrode plate and a negative electrode plate, the collectormember includes: a first connecting portion which electrically connectsto a first electrode tab which is provided in a corresponding one of thepositive electrode plate and the negative electrode plate of the firstelectrode body element, and a second connecting portion whichelectrically connects to a second electrode tab which is provided in acorresponding one of the positive electrode plate and the negativeelectrode plate of the second electrode body element, wherein the firstelectrode tab and the second electrode tab are of a same polarity aseach other, the sealing plate has a longitudinal direction and a shortdirection perpendicular to the longitudinal direction, and the secondregion is located between the first connecting portion and the secondconnecting portion in the short direction of the sealing plate.